Continuous casters of the curved type are in common use today and, for larger strands such as blooms and slabs, generally include a curved roller apron which is followed by a withdrawal and straightening unit. The roller apron supports the strand issuing from the continuous casting mold. One of the functions of the withdrawal and straightening unit is to bend and thereby straighten the strand as it advances out of the curved roller apron.
In the event of metal breakout occurring at a cast strand, the further casting of the strand is discontinued. The trailing end of the strand is normally severed from the remainder of the strand and lifted out of or otherwise removed from the caster together with the first section of the roller apron. Severing of the trailing end of the strand from the remainder thereof is generally necessary since the solidified molten metal in the region of the trailing end of the strand binds the strand to the roller apron and makes it impossible to move the strand in the caster. By severing the trailing end of the strand, the remainder of the strand then becomes free to move.
It is necessary that the strand be allowed to cool down somewhat before the trailing end is severed since the heat which would otherwise emanate from the strand would make it difficult for personnel to work adjacent to the strand. In addition, the section of the strand remaining in the caster, after removal of the trailing end, undergoes further cooling during the severing operation. Since the resistance to bending of the strand increases with decreasing temperature, it may happen that the cooled section of the strand remaining in the caster after the severing operation can no longer be bent by the withdrawal and straightening unit. This means that the cooled section of the strand remaining in the caster cannot be removed from the latter in the conventional manner employed during a casting operation. Thus, it is currently the practice to cut the cooled section of the strand into relatively short lengths and to remove the cooled section of the strand from the caster piece by piece.
One manner which is used for carrying out this procedure involves lowering one of the lower rollers of the withdrawal and straightening unit and thereafter bringing a protective element, such as a sheet, into position over the lowered roller from laterally of the caster. Subsequently, burners for cutting the strand are inserted between the protective element and the cooled strand. By alternately cutting the strand and then advancing the strand in the casting direction, the strand is cut into relatively short lengths which are removed from the caster one by one.
The procedure outlined above has several disadvantages. To begin with, there exists the possibility of damage to the expensive drive rollers and their bearings by the burners and/or by molten steel generated by the cutting operation. Furthermore, there is no guarantee that slag generated by the cutting operation will not remain in the withdrawal and straightening unit. In addition, due to the fact that the movable lower roller of the withdrawal and straightening unit must be lowered through a substantial distance, the withdrawal and straightening unit, as well as the foundation therefor, become expensive. Finally, since it is necessary to make several cuts with the burners, the downtime of the caster is large.